Electrically-driven vehicles are increasingly popular because they use no gasoline which at times has been unavailable to the public and is becoming progressively more expensive. Electrically-driven vehicles are also quiet in operation and non-polluting of the surrounding atmosphere.
Electrically-driven tricycles powered by on-board storage batteries are suited for short distance commuter use. Its three wheels provide a degree of stability and safety not found in bicycles or motorcycles. It can be operated by people of all ages and by city dwellers who desire inexpensive, clean and quiet transportation. When fitted with a platform or basket, it is especially suited for neighborhood shopping and for the carrying of luggage, for mail service, for messengers, maintenance men and the like. Vehicles of this type are described in U.S. Pat. Nos. 3,369,629, 3,598,195 and 3,759,339.
Tricycles also have the advantage that one rear wheel can be used for an electrified drive while the other rear wheel can be used for the conventional pedal, sprocket and chain drive. By using the pedal drive, the range of an electrified vehicle can be extended before battery re-charging is necessary. The foot pedals can be used for starting heavy loads and on upgrades to prevent excessive current drain from the batteries. Handbrakes and coaster brakes as are usually found on tricycles and bicycles can be retained. Additionally, where a permanent magnet direct current motor is used, it is possible to achieve dynamic braking from the motor. Also, during periods of dynamic braking, it is possible to use the motor output to recharge the batteries which drive the motor in conventional operation.
The light weight of a tricycle, which is generally advantageous from the standpoint of conservation of the battery-stored energy, allows very rapid acceleration of the vehicle when the battery source is connected to the electric motor. However, with the electric motor connected to only one of the two rear wheels, rapid development of speed can have the disadvantage of causing the tricycle to swerve from its path of travel. While a skilled and experienced operator of the tricycle can maintain his proper course, there is a sensation of sidewise tugging and imbalance present because of the unevenness of transmission of power between the two rear wheels.
Electrified adult tricycles have been constructed to operate at several discrete speed levels. This allows proper selection of speeds by the operator in accordance with immediate driving conditions. For example, riding in city traffic may require a lower speed than riding in open suburban and rural areas. In the current art where the forward speed of the tricycle is varied by adjusting the voltage to the motor in discrete steps, there is a short interval when no voltage is applied to the motor as the switching device is transferred from a lower to a higher level and vice-verse. The forward motion of the tricycle is jerkey, uneven and uncomfortable for the rider when speed levels are changed, and short periods without electrical power occur.
Additionally, present electrified adult tricycles provide jerky and uncomfortable performance when running downhill. This can occur when the back electromotive force generated in the motor on downhill running exceeds the voltage available from the battery supply. At such speed and condition, the motor acting as a generator drives current back into the battery. In the process dynamic braking, desirable or not, is provided for the vehicle. The braking thus produced causes the vehicle to slow down; when the back electromotive force falls below the applied battery voltage, the motor reverses its generator action, acts again as a motor, and drives the bike forward at increasing speed until the process repeats itself. The result is an unpleasant ride.
What is needed is an electrified adult tricycle which can be driven either electrically or by foot pedal drive or by both simultaneously. Also, the tricycle should start and operate smoothly under electric power. It should have multispeed capability to adjust to riding conditions and provide high economy and long range in operation.